Calculating coil parameters based on required voltage and amps.

[Dano000]

Hi everyone,

First post

I am currently designing a small wind turbine and was wondering if there is some sort of formula which can be applied to calculating a coils inner and outer diameter, thickness, amount of turns and gauge based on the voltage and amperage I need.

I am wanting to have either 24 (± 10%?) or 48 (± 5%?) volts and preferably between 5 - 10 amps.

I would think that it would have to do something with the strength of the rotor magnets as well, the ones I found are class N50 neodymium magnets, which I am told are ideal for turbines due to the incredible strength.

The turbine I am making is designed to accommodate 3 coils, for 3 phase AC power.

I am told 3 phase is most efficient, so that's why, but since it's going to be rectified so that it can be stored in a battery bank, is it worth it having 3 phase?

I've made the design a "VAWT", just want to test out how efficient it will be

Thanks!
Dano

 

[LionelHutz]

If you have the magnets then you already have the coil dimensions. Just wind-up a coil, fit it into the air gap and give it a spin with the volt meter attached. The voltage will vary directly with rpm so you can figure out your voltage per turn at the exected operating rpm. The wire resistance will tell you how much voltage drop at your desired current which may require extra turns to compensate for.

Try reading the wind info at

http://www.otherpower.com

if you still don't get it.

 

[Dano000]

I see, OK thanks for that!

But, surely there is a formula based on the magnetic field strength of the magnet and desired voltage to find the diameter of the coil and how many windings and what gauge? Or am I mistaken?

Thanks!
Dano

 

[ScottyUK]

Have a look for an undergraduate-level electrical machiens or electrical principles text book. This forum is too restrictive in its ability to enter equations and Greek characters to help directly, but you are correct: there are formulae which will either give you a close approximation or a fairly accurate result depending on how good your input data is and how much accuracy you need.


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If we learn from our mistakes I'm getting a great education!

 

[OperaHouse]

You forgot the most important factor......SPEED. Voltage varies with speed. That you can't control.

Really, you should go to otherpower. They are the leading source on the internet for trailing edge technology. It doesnt bode well for the future of RE when a group like this can't give up using 1920's techno;ogy.

 

[waross]

First investigate the effect of the length of the magbetic circuit on the flux density.
Then look at the effect of an air gap in the magnetic circuit.
Investigate the effect of speed on the voltage induced in a wire moving in a magnetic field.
Then design the magnetic circuit. Determine how the dimensions of a coil that will fit in the space that you have provided for windings.
Repeat this process until you find a solution that you are happy with.
There are a lot of formulas, some rules of thumb and a lot of trial and error in a design such as yours.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

OperaHouse - You have some control over the speed when doing the blade design. You should have a power vs speed curve once the blades are designed.

 

[Dano000]

Alright, off to a Uni Library it is

Thanks guys!

As for the speed of the voltage are you talking about the current or something else? I've never heard of voltage having different speeds, if so what is the unit?

Thanks!
Dano

 

[LionelHutz]

Speed as in the rpm of the generator.

 

[OperaHouse]

You say..."I am wanting to have either 24 (± 10%?) or 48 (± 5%?) volts" without stating at what design rpm the generator will turn. In a wind generator you want the blades to begin turning and creatin a voltage below the battery voltage. At higher speeds the rpm will be limited by battery loading if the battery is large enough and by a dump load regulator.